Can't access MediaNET MMS

I have an LG Shine right now, before then I had a Razor V3r and in both I have the same problem of not being able to send MMS messages or access the internet. It's really frustrating because I did call customer service and they told me that my internet was pay per use, but what good is that? On my Shine it's telling me Connection Failed when I try to access the web, and for the MMS it tells me network unavailable. Any idea?